缩略语

CIDCalling Identify Delivery主叫识别信息传送DACDiscretionary Access Control自主存取控制DCSDistributed Control System分布式控制系统DTMFDual-Tone Multi-Frequency双音多频FSKFrequency-Shift Keying移频键控GALGraphics Abstract Layer图形抽象层GFSKGuassian Freque     

吉比特MAC接口IP软核的分析与研究

MAC(Media Access Control)层位于网络结构七层协议中的数据链路层,控制局域网中的多个节点对共享介质的访问,保证相邻节点之间数据的可靠传输。本文介绍一种吉比特MAC接口的结构,该MAC采用基于描述符传输的DMA(Direct Memory Access)和双通道的MTL(MAC Transaction Layer),在半双工模式下支持10/100 Mb/s、全双工模式下支持10/100/1 000 Mb/s的网络数据传输速率。     

基于Mixer Layer的人脸表情识别

目前人脸表情识别研究多数采用卷积神经网络(CNN)提取人脸特征并分类, CNN的缺点是网络结构复杂, 消耗计算资源. 针对以上缺点, 本文采用基于多层感知机(MLP)的Mixer Layer网络结构用于人脸表情识别. 采用数据增强和迁移学习方法解决数据集样本不足的问题, 搭建了不同层数的Mixer Layer网络. 经过实验比较, 4层Mixer Layer网络在CK+和JAFFE 数据集上的识别准确率分别达到了98.71%和95.93%, 8层Mixer Layer网络在Fer2013数据集上的识别准确率达到了63.06%. 实验结果表明, 无卷积结构的Mixer Layer网络在人脸表情识别任务上表现出良好的学习能力和泛化能力.     

Anwell公司推出双层DVDR生产系统DVDR Smart Line Twin-DL

宏威数码机械有限公司单面双层DVDR生产线(DVDR Smart Line Twin Dual Layer)是一条采用先进Inversed Stuck DVDR单面双层(IS)生产概念设计的快捷双头生产系统。系统TOYO STAD-3注塑机,宏威数码的SPORTS VT-IV旋涂机及SMART-II下游生产线组合而成。配合宏威数码公司独特的母盘及DVDR Dual Layer生产工艺,生产 DVDR Dual Layer产品最快生产周期每片只需3．0秒,即每条线每小时最高可生产1200片。为使设备达到最佳的稳定     

图形精灵Paint Shop Pro for Wn95——介绍图形处理器Paint Shop Pro4.1

Paint Shop Pro4.1(下称PSP)是JASC公司新近推出的一款基于Windows95的强力图形处理器。它最近荣获了第四届Ziff—Davis共享软件奖之年度最佳程序奖。除了支援超过卅个文件格式外,它也提供多层次(Layer)处理功能,让您编辑多个Layer后结合为一。并且,可以让每个Layer都拥有不同的特殊效果,使您在编辑上倍感方便自如,修改时也可以仅针对某个Layer进行修改而不必全图重新制作!另外,内建的截图功能让您截取任何屏幕画面进行编排和修整,再利用其多种特殊效果及制作网页用按钮等功能制作专业级的图案。如果您需要一个专业级的绘图软件却又无多余的硬盘空间,那么,Paint Shop Pro4.1将是您最佳的选择。     

新品视线

HP两款交换器新品 让你用现在交换未来 HP AdvanceStack交换器 800T HP AdvanceStack交换器800T 是一个高性能的分段交换器,适用 于服务器区的网络连接。这台设备提供8个100Base-T端口,具有8个凹式收发器插槽,能支持任何组合的UTP(100Base-TX)或光纤(100Base-FX)收发器,其标准配置包括4个已经安装的UTP收发器。 它所提供的卓越性能,来自一个高速lGbps总线,可在任何端口上进行全双路操作。此外,它还有一个多交换器端口线槽,可将多个端口结合为一条速度更高的各交换器之间的单一连线。10/100Base-T自动感应也可在所有100Base-TX端口上配置。 随机提供功能强大的自动流通优化软件,包括Layer3交换(Layer 3 Switching)、Layer 3协议筛选(Layer 3 Proto-     

一种卫星移动通信中的L/P跨层设计

针对卫星移动信道,提出了一种基于链路层(Link Layer)的混合自动请求重传(HARQ)技术联合物理层(Physical Layer)自适应编码调制(AMC)技术的L/P跨层设计;在Nakagami-m信道模型中验证其性能,并与非跨层设计结果作了对比。理论分析及仿真比较结果表明,这种跨层设计可以综合有效地优化卫星移动通信性能。     

3Com VPN又进一步

3Com近日推出L2TP(Layer 2 Tunneling Pro-tocol)和扩展型IPsec(Internet Protocol Security)最新强化软件,从而进一步为用户扩展了VPN解决方案。把这些新款强化软件应用于3Com NETBuicder产品系列和Total Control远程访问平台产品系列,企业和网络服务提供商(NSP)现在就可以按照基于标准的VPN解决方案去构建新网或升级其原有网络。 L2TP标准目前已被Internet工程分会(IETF)采纳,它是在WAN基础设施中建立网络“隧道”的标准。IPsec标准包括许多安全性标准,如加密、数字化签证和密钥管理。IPsec和L2TP相结合,就可在公用的IP网络设施中产生基于标准的安全的WAN连接。 L2TP和IPsec包括在11.1版本的NETBuilder软件中,     

“佳能杯图像大师大奖赛征稿启事”

数字作图和物理作图的根本区别在哪儿?一个画家开始在画布上作画时，在他心中图画的基本构思已经形成。但是如果错了就只能再打开一张画布．重新开始!可是在Photoshop中，这种情况永远不会出现。只是因为有了Layer(层)的引入。你的图像构思也许有三大件组成。如：房屋布局，家具和人物。你可以把这三项分别定为三个Layer，如果你在修改人物Layer时，出现了致命的错误，不要紧，     

Paint Shop Pro 8.0 Beta

Paint Shop Pro是可与photoshop媲美的绘图软件。除了支持超过三十个文件格式外，它也提供Layer功能，让您编辑多个Layer后再结合为一并且可以让每个Layer都拥有不同的特殊效果，使您在编辑上方便许多，修改时也可以仅针对某个Layer进行修改而不必全圈重新制作!另外，内建的画面颉取功能让您颉取任何屏幕画面进行编辑，再利用其多种特殊效果及制作网页用按钮等功能制作专业级的图案。     

对网络流量管理与拥塞管理的研究

分析了计算机网络拥塞产生的原因及影响,研究了网络流量管理与拥塞管理的策略,提出了采用流量管理技术来增强网络层的流量控制功能,控制网络拥塞的产生,采用拥塞管理策略,优化网络资源的分配,解决网络资源的竞争,为有不同服务需求的网络业务提供有区别的服务,从而有效地控制网络拥塞。     

改进的退避算法在战术业务流中应用研究

研究战术的网络业务流问题。针对传统的网络退避算法由于网络信道访问频率过大,容易造成节点缓存队列拥塞等问题,特别是退避算法中的参数选择问题严重影响网络性能传输。提出了一种改进的退避算法应用于战术网络业务流中。改进的算法首先为结点引入适当的竞争系数,使得对于信道的访问可以根据当前网络的突发状态合理分派,同时根据网络状态和冲突节点发生情况,对竞争窗口大小分别采用线性和多重下降等方式进行动态调整,有效地改善网络的性能。仿真结果表明,改进后的退避算法具有较好的性能,有效降低了网络信道访问冲突发生概率,提高了网络系统的吞吐量。     

基于协调博弈的交通拥塞传播临界值研究

为深入分析交通网络的拥塞扩散过程,得出交通拥塞传播的临界值,提出了交通拥塞传播的协调博弈模型。通过网络个体之间的协调博弈,从出行者面对拥塞的决策行为出发,描述了交通网络的拥塞扩散过程。通过网络邻居之间的行为传递,形成了交通网络的拥塞扩散模型,并利用概率母函数方法推导了交通拥塞扩散的临界条件。最后构建了交通通塞的仿真系统,并通过路网结构、节点度分布等参数对交通拥塞进行了仿真分析。仿真实验结果与解析分析结果一致,并能反映交通拥塞动态过程信息,结果表明交通拥塞扩散的临界条件关键在于拥塞节点对周边正常节点的影响力,当局部交通拥塞对周边节点的影响力达到一定程度时,可能导致大规模交通拥塞的出现。     

Urban traffic congestion propagation and bottleneck identification

Bottlenecks in urban traffic network are sticking points in restricting network collectivity traffic efficiency. To identify network bottlenecks effectively is a foundational work for improving network traffic condition and preventing traffic congestion. In this paper, a congestion propagation model of urban network traffic is proposed based on the cell transmission model （CTM）. The proposed model includes a link model, which describes flow propagation on links, and a node model, which represents link-to-link flow propagation. A new method of estimating average journey velocity （AJV） of both link and network is developed to identify network congestion bottlenecks. A numerical example is studied in Sioux Falls urban traffic network. The proposed model is employed in simulating network traffic propagation and congestion bottleneck identification under different traffic demands. The simulation results show that continual increase of traffic demand is an immediate factor in network congestion bottleneck emergence and increase as well as reducing network collectivity capability. Whether a particular link will become a bottleneck is mainly determined by its position in network, its traffic flow （attributed to different OD pairs） component, and network traffic demand.     

Adaptive congestion control scheme in mobile ad-hoc networks

In the past, several authors have expressed their concerns over the poor congestion control in mobile wireless ad-hoc networks using traditional reference layer model. Many solutions were proposed to handle growing traffic and congestion in the network, using link layer information. Existing solutions have shown difficulties in dealing with congestion with varying packets drop. Moreover, ensuring the superior performance of congestion control schemes with traditional referenced layer model is a challenging issue, due to quick topology changes, dynamic wireless channel characteristics, link-layer contentions, etc. In this paper, we propose an effective cross-layer adaptive transmission method to handle the congestion in mobile wireless ad-hoc networks adequately. Simulation results exemplify the usefulness of the proposed method in handling congestion, and yields better results compared to existing approaches.     

基于综合度量的Ad Hoc网络跨层路由协议

Ad Hoc网络路由协议普遍采用最短路径准则,无法有效支持多速率传输并容易导致网络局部拥塞。针对该问题,利用协议栈跨层设计的思想,提出一种基于综合度量的路由协议SMRP。该协议综合考虑链路速率值、MAC竞争度和网络队列长度多种因素选择路径,能有效利用多速率传输能力,避开拥塞节点。仿真实验结果证明,该协议能从网络吞吐量、分组时延等方面有效提高网络性能。     

Design and Performance Evaluation of a Distributed Contention Control (DCC) Mechanism for IEEE 802.11 Wireless Local Area Networks

This paper focuses on the design and performance evaluation of a new mechanism, named Distributed Contention Control (DCC), for the adaptive contention reduction in LAN networks that utilize random access MAC protocols. The proposed mechanism could be executed on the top of a preexistent access protocol, with no additional overhead introduced. Specifically, we consider the IEEE 802.11 wireless LAN (WLAN). The DCC mechanism requires a simple and rough estimate of the contention level, and this can be achieved by estimating any parameter, directly connected with the amount of contention on the shared channel. The main characteristics of the proposed mechanism are represented by its simplicity, integration with the Standard, complete distribution, absence of overheads, and prompt reaction to changes in the network congestion. The protocol automatically adapts to the network congestion by monitoring the channel contention level through the estimation of the contention parameter. In this paper we show that the information needed for the contention estimation is already available to a 802.11 station, with no additional costs. Simulation experiments to evaluate the performance of an IEEE 802.11 WLAN, with and without the DCC mechanism, have been carried out. Results confirmed the effectiveness of the DCC mechanism in improving the performance, stability, and congestion reaction of the IEEE 802.11 access scheme. The DCC mechanism also provides a simple way to implement a distributed priority mechanism.     

基于物联网的城市道口机动车智能监控和行为检测系统

物联网架构的城市道口机动车监控和行为分析系统在传统的物联网定义基础上,提出了包含感知／发布层、智能中间层、网络层、服务层和应用层的智能监控架构、以高清网络监控相机为采集终端,使用自行开发的图像分析算法和软件实现了道路拥堵状态判定以及多目标车辆追踪,实时采集视频流中道口监控区域内车辆移动轨迹、速度、前方道路拥堵状态等基本参数;在通信层使用3G／Wi—Fi等高速无线通信技术与有线通信相结合实时传输关键参数和监控图像,应用层使用自行开发的中心监控软件平台实现了对关键数据的存储、统计、业务应用的服务支持和管理,应用层针对电子警察、智能交通监控和信息发布展开,结合交通控制信息和我国交通法规为违章实时判定、交通信息采集等提供了基础、     

A fairness analysis of LAN/WAN protocol relays

Functional standardization activities in ISO and in regional workshops are currently addressing network layer relays for the interconnection of several types of subnetworks. Relay systems are critical systems in the overall performance of the network because they are the points where network congestion can be built up or avoided. Particularly, when the interconnected subnetworks have very dissimilar bandwidths, congestion control becomes a very important issue in relay systems design. This paper addresses the problem of congestion control in relay systems for LAN/WAN interworking. Congestion control deals with the avoidance of collapse situations in intermediate systems due to traffic overload. It deals also with the guarantee of fairness in resource utilization, considering user needs of communication services expressed in terms of Quality of Service (QoS) parameters. To ensure congestion collapse avoidance and fairness, a channel service algorithm is proposed. Simulation results show that, in a situation of overload and for different traffic patterns with different QoS requirements, the relay's channel service and acknowledgment algorithms can guarantee justice in resource utilization and the expected QoS among the active channels.     

A family of mechanisms for congestion control in wormhole networks

Multiprocessor interconnection networks may reach congestion with high traffic loads, which prevents reaching the wished performance. Unfortunately, many of the mechanisms proposed in the literature for congestion control either suffer from a lack of robustness, being unable to work properly with different traffic patterns or message lengths, or detect congestion relying on global information that wastes some network bandwidth. This paper presents a family of mechanisms to avoid network congestion in wormhole networks. All of them need only local information, applying message throttling when it is required. The proposed mechanisms use different strategies to detect network congestion and also apply different corrective actions. The mechanisms are evaluated and compared for several network loads and topologies, noticeably improving network performance with high loads but without penalizing network behavior for low and medium traffic rates, where no congestion control is required.